To ignite a propellant charge in a cartridge case, it is known to use primer caps. FIGS. 1 and 2 each show in section, the rear end of a casing of a cartridge case according to the prior art with the primer cap in place before (FIG. 1) and after (FIG. 2) ignition.
A cylindrical case 1 is provided at its rear end with a primer receiving pocket or chamber 4 in the form of a cylindrical recess. Flash holes 11 in a rear portion of the case terminate in the top of primer receiving pocket 4, said flash holes communicating with a propellant charge, not shown, inside a cavity in the case 1. A primer cap is mounted flush in the primer receiving pocket 4. The primer cap consists of a cup-shaped capsule 6 with a planar capsule bottom and a cylindrical side wall. A primer charge 2 is pressed into the interior of the capsule 6 on the bottom of the capsule. Above primer charge 2 is an anvil 8 with openings for passage of gases. The primer cap is anchored in the case 1 by annular riveting 3.
When the firing pin 5 of a weapon strikes the bottom of the capsule (see FIG. 2), the capsule is deformed. This suddenly compresses primer charge 2 between the bottom of the capsule and anvil 8, causing the charge to explode. The resulting hot gases pass through the openings in anvil 8 to flash holes 11 and from there to the propellant charge, not shown, and then ignite the charge.
The cartridge cases to be fired in handguns must exhibit gas tightness in the direction of the breech, in order to reliably prevent any danger to the shooter or damage to the weapon. In particular, pollutant-free primer caps are richer in gas than the former types containing particles and in part, pollutants. As a result, much higher gas pressures develop during firing in the area of the primer receiving pocket, with a very brief pressure rise. This can cause gas to escape in the vicinity of the primer cap, which can be seen, in particular, in unlocked weapons with a breech and a rigid, permanently attached firing pin.
This gas escape is shown as an example in FIG. 2. The material of the capsule bottom is plastically deformed to a great extent in critical area 7 between the fixed anvil 8 of the primer cap and firing pin 5 which cannot move back because of its rigid connection with the lock at the moment of ignition. As a result of the high gas pressure from the pollutant-free primer cap, the material of the capsule bottom can be stressed above the limit of elongation at rupture (thinning leading to a break) in area 7, which can lead to the escape of gas in the direction of the breech or to a migration of the primer cap and hence to a leak or a "back blast".
Primer caps like those described above are shown for example in DE-OS 20 04 506 and DE-OS 27 08 525.